Please don't post the same question twice, because it only result in an unneeded duplication of support effort for us, with no benefit whatsoever for you. We reply to all messages so, there's no need to post them multiple times.
You have been answered here:
http://www.fsdreamteam.com/forum/index.php?topic=5080.msg58790#msg58790As explained, many times already, when you don't have buildings, it's NOT "like Trial mode". Trial mode is not like that. Trial mode is ALL buildings working in full, disappearing after 5-6 minutes, and a clearly indications of a Trial period is beginning, when you first go to the airport.
So, your problem doesn't have anything to do with activation or registration or anything like that because, if you lose your activation for any reason, the scenery will NOT "just disappear", but it will revert to Trial mode, running for 5-6 minutes at time. Just to be more explicit: you can have an *unlimited* number of 5-6 minutes periods, the Trial mode doesn't ever expire.
If you simply don't see buildings, the problem is entirely different: there's something wrong in your system that is preventing the software to run.
If it happens again, note if you have the "Addon Manager" AND the "Couatl powered products" menus under the "Addons" menu. If you have only one, nothing will work and, depending which one is missing, the troubleshooting procedure is entirely different.